vttablet api distributed transaction changes

[harshit-gangal]

Description

This PR make few changes to the distributed transactions API on the vttablet

• Prepare API to rollback and release the transaction when
  • no DML is executed on the transaction (no error to return)
  • DML executed on a reserved connection (return error as well to fail the prepare)
• CommitPrepare API to log a warning if failed to commit a transaction
• StartCommit API to fail if executed on a reserved connection and mark the transaction state to ROLLBACK

Related Issue(s)

• RFC: Atomic Distributed Transactions #16245

Checklist

• Tests were added or are not required
• Did the new or modified tests pass consistently locally and on CI?
• Documentation was added or is not required

Deployment Notes

[vitess-bot]

Review Checklist

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• Ensure that the Pull Request has a descriptive title.
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[codecov]

Codecov Report

Attention: Patch coverage is 95.83333% with 1 line in your changes missing coverage. Please review.

Project coverage is 68.76%. Comparing base (4a89749) to head (921c55f).
Report is 1 commits behind head on main.

Files	Patch %	Lines
go/vt/vttablet/tabletserver/dt_executor.go	95.00%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main   #16506      +/-   ##
==========================================
+ Coverage   68.74%   68.76%   +0.01%     
==========================================
  Files        1556     1556              
  Lines      199705   199715      +10     
==========================================
+ Hits       137292   137334      +42     
+ Misses      62413    62381      -32     

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